1. Field of the Invention
The present invention relates to magnetic head inspecting apparatuses, and more particularly to magnetic head apparatuses for testing a magnetic head loaded to a magnetic disk apparatus.
2. Description of the Related Art
In recent years, further improvements in recording density, high speed transfer of data, and high-speed rotation of spindles have been required for magnetic disk apparatuses. To attain such requirements, a Magnetic Resistive (MR) head has been used which can obtain a reproduced signal of high output level, without relation to the number of rotations (circumference speed) of a disk medium. A signal recording system for such magnetic disk apparatuses has been mainly based on the Partial Response Maximum Likelihood (PRML) technique, however, a fluctuation of signal levels has been shown to increase considerably using this technique progress in disk recording density. Recently, to account for this fluctuation, data has been conventionally read through an error correction method which utilizes a Maximum Likelihood (ML) process. When sufficient performance cannot be obtained by testing and evaluating with the magnetic head testing apparatus whether the MR head has an expected reproducing performance, investigation should be performed to analyze and pursue causes.
Known magnetic head testing apparatuses, however, experience problems with the amount of time required for investigative testing. Longer times are required for the testing work because signal waveforms of the magnetic head are displayed for a visual check and analysis of the waveforms by inputting the reproduced signal of the MR head to a measuring instrument such as an oscilloscope or the like.
Moreover, since the waveform read-out includes electronic noise, which can randomly change during any reading, and a medium noise, which can randomly change during any writing, it is difficult to observe how well the magnetic head has performed a writing. Additionally, the waveforms often lose their phase characteristics, and therefore it has also been impossible to observe overlap of a plurality of waveforms.